Coil component

ABSTRACT

The coil component includes a magnetic body containing a metallic material and a resin material, a coil conductor embedded in the magnetic body, and a pair of outer electrodes electrically connected to ends of the coil conductor. The coil conductor includes an exposed portion at each end portion of the coil conductor, and a covered portion covered with an insulating substance disposed between the exposed portions. The covered portion is disposed inside a face of the magnetic body on which the outer electrodes are disposed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.15/820,059 filed Nov. 21, 2017, which claims benefit of priority toJapanese Patent Application No. 2016-228242, filed Nov. 24, 2016, theentire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a coil component and more particularlyto a coil component that includes a magnetic body and a coil conductorembedded in the magnetic body.

BACKGROUND

In recent years, with an increase in the performance and a decrease inthe size of electronic equipment, there has been a demand for smallerelectronic components for use in electronic equipment. Coil components,such as inductors, are not exceptions and are also being decreased insize by various means.

For example, in order to decrease the electrical resistance of a leadend of a coil conductor and an external terminal electrode, thethickness of a conducting wire has hitherto been increased to increasethe contact area between the lead end of the coil conductor and theexternal terminal electrode. In this method, however, a coil componentis disadvantageously increased in size in order to achieve the desiredinductance. To address the problem, International Publication WO2015/115318 discloses a coil component that includes a coil conductorembedded in a compact formed of a composite material containing amagnetic material powder and a resin, wherein a lead end of the coilconductor is obliquely cut to increase the contact area of an externalterminal electrode.

In such a coil component including a magnetic body formed of a compositematerial containing a metallic material and a resin material, an outerelectrode is generally formed by applying a silver paste containing athermosetting resin to the magnetic body by dip coating. In such amethod, however, the resin between silver particles disadvantageouslyincreases the electrical resistance of the outer electrode and decreasesproduct efficiency. Furthermore, the formation of a thick silver filmincreases the cost.

To address these problems, an outer electrode can be formed by directplating on a magnetic body. A magnetic body formed of a compositematerial containing a metallic material and a resin material has arelatively low specific resistance, and therefore a wire for a coilconductor is covered, for example, with an insulating resin to ensureinsulation from an inner coil conductor. In the formation of an outerelectrode by plating, as described above, particularly in the formationof an outer electrode by barrel plating, in order to provide the outerelectrode with good characteristics, it is needed to ensure electricalcontinuity between both end faces of a magnetic body via a coilconductor in a short time after the beginning of plating. Morespecifically, a magnetic body should be electrically connected to a coilconductor in a short time over an insulating film surrounding the coilconductor. A delay in connection may result in a change in the surfaceoxidation state of a magnetic body or deposition of impurities on amagnetic body, reduce electricity supply from a medium, cause variationsin plating thickness between coil components, or increase the specificresistance of an outer electrode.

SUMMARY

Thus, it is an object of the present disclosure to provide a coilcomponent that includes a coil conductor embedded in a magnetic bodycontaining a metallic material and a resin material, wherein the coilcomponent includes an outer electrode with good characteristics.

As a result of extensive studies to solve the problems, the presentinventor has arrived at the present disclosure by finding that, in acoil component that includes a coil conductor embedded in a magneticbody containing a metallic material and a resin material, an outerelectrode can be provided with good characteristics by removing aninsulating film at an end portion of the coil conductor to expose thecoil conductor and thereby ensuring electrical continuity between thecoil conductor and the magnetic body in a short time after the beginningof plating treatment.

According to a first aspect of the present disclosure, there is provideda coil component that includes a magnetic body containing a metallicmaterial and a resin material, a coil conductor embedded in the magneticbody, and a pair of outer electrodes electrically connected to ends ofthe coil conductor. The coil conductor includes an exposed portion ateach end portion thereof and a covered portion covered with aninsulating substance disposed between the exposed portions. The coveredportion is disposed inside a face of the magnetic body on which theouter electrodes are disposed.

According to a second aspect of the present disclosure, there isprovided a method for producing a coil component that includes amagnetic body containing a metallic material and a resin material, acoil conductor embedded in the magnetic body, and a pair of outerelectrodes electrically connected to ends of the coil conductor. Themethod includes treating a peripheral portion of the coil conductor bylaser irradiation, the peripheral portion being exposed at a surface ofthe magnetic body, and then forming the outer electrodes by platingtreatment.

The present disclosure can provide a coil component that includes amagnetic body containing a metallic material and a resin material, acoil conductor embedded in the magnetic body, and a pair of outerelectrodes electrically connected to the coil conductor. An end portionof a lead portion of the coil conductor comes out from an insulatingsubstance film, and at least part of the exposed portion is disposedinside the magnetic body. Thus, the outer electrodes have low resistanceand little variation in thickness.

Other features, elements, characteristics and advantages of the presentdisclosure will become more apparent from the following detaileddescription of preferred embodiments of the present disclosure withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an electronic componentaccording to an embodiment of the present disclosure;

FIG. 2 is a perspective view of the electronic component illustrated inFIG. 1 without outer electrodes and an insulation film;

FIG. 3 is a schematic cross-sectional view of the body illustrated inFIG. 2 parallel to the LW-surface on the periphery of the coilconductor;

FIG. 4 is a schematic plan view of the periphery of the coil conductoron an end face;

FIG. 5 is a SEM image of a laser-irradiated body surface in an example;

FIG. 6 is a SEM image of a laser-irradiated body surface in an example;and

FIGS. 7A to 7D are schematic plan views of the periphery of the coilconductor after laser irradiation in an example.

DETAILED DESCRIPTION OF EMBODIMENTS

Coil components according to embodiments of the present disclosure willbe described in detail below with reference to the accompanyingdrawings. However, the shape and arrangement of each coil component andeach constituent according to the embodiments are not limited to thoseillustrated in the drawings.

FIG. 1 is a schematic perspective view of a coil component 1 accordingto the present embodiment. FIG. 2 is a schematic perspective view of abody 6 of the coil component 1, exposed without the outer electrodes 31and 32, and insulation film 41, as shown in FIG. 1.

As illustrated in FIGS. 1 and 2, the coil component 1 according to thepresent disclosure has a generally rectangular parallelepiped shape.Roughly speaking, as illustrated specifically in FIG. 2, the coilcomponent 1 includes a magnetic body 11, a coil conductor 21 embedded inthe magnetic body 11, and outer electrodes 31 and 32. The magnetic body11 and the coil conductor 21 embedded in the magnetic body 11 constitutethe body 6. The body 6 has a generally rectangular parallelepiped shape,has two opposite end faces 15 and 16, and has a first side surface 17, asecond side surface 18, a third side surface 19, and a fourth sidesurface 20 between the end faces 15 and 16. The outer electrodes 31 and32, as shown by hatching in FIG. 1, are disposed on the end faces 15 and16, respectively, and extend to a portion of the fourth side surface 20.Thus, the outer electrodes 31 and 32 have a substantially L-shaped crosssection. One end 22 of the coil conductor 21 is electrically connectedto the outer electrode 31, and the other end 23 is electricallyconnected to the outer electrode 32. As further shown in FIG. 1, aninsulation film 41 is disposed in a region on the side surfaces of thebody 6 where no outer electrode is disposed.

The magnetic body 11 contains a metallic material and a resin material.Preferably, the magnetic body 11 is formed of a composite material of ametallic material and a resin material.

The resin material may be, but is not limited to, an organic material,such as an epoxy resin, a phenolic resin, a polyester resin, a polyimideresin, or a polyolefin resin. The resin materials may be used alone orin combination.

The metallic material may be, but is not limited to, iron, cobalt,nickel, or gadolinium, or an alloy containing at least one thereof.Preferably, the metallic material is iron or an iron alloy. The ironalloy may be, but is not limited to, Fe—Si, Fe—Si—Cr, or Fe—Si—Al. Themetallic materials may be used alone or in combination. The metallicmaterial may contain at least one metal selected from palladium, silver,and copper, as well as the metal described above.

The metallic material is preferably a powder, that is, a metal powder.The metal powder may be a crystalline metal (or alloy) powder or anamorphous metal (or alloy) powder. The metal powder may be coated withan insulating substance. The insulating substance on the surface of themetal powder can increase the specific resistance of the magnetic body11.

The metallic material content of the magnetic body 11 is preferablyapproximately 50% or more by volume, more preferably approximately 60%or more by volume, still more preferably approximately 70% or more byvolume. A metallic material content in this range results in improvedmagnetic characteristics of a coil component according to an embodimentof the present disclosure. The metallic material content of the magneticbody 11 is preferably approximately 95% or less by volume, morepreferably approximately 90% or less by volume, still more preferablyapproximately 87% or less by volume, still more preferably approximately85% or less by volume. A metallic material content in this range resultsin an increased specific resistance of the magnetic body 11. In oneembodiment, the metallic material content of the magnetic body 11 maypreferably range from approximately 50% to 95% by volume, morepreferably approximately 60% to 90% by volume, still more preferablyapproximately 70% to 87% by volume, still more preferably approximately70% to 85% by volume.

The metal powder preferably has an average particle size ofapproximately 5 μm or more, more preferably approximately 10 μm or more.A metal powder having an average particle size of approximately 5 μm ormore, particularly approximately 10 μm or more, is easy to treat. Themetal powder preferably has an average particle size of approximately100 μm or less, more preferably approximately 80 μm or less. A metalpowder having an average particle size of approximately 100 μm or less,particularly approximately 80 μm or less, can have a high filling rateand improve the magnetic characteristics of the magnetic body 11. Theterm “average particle size,” as used herein, refers to the averageparticle size D50 (the particle size at a cumulative percentage of 50%by volume). The average particle size D50 can be measured with a dynamiclight scattering particle size analyzer (UPA manufactured by NikkisoCo., Ltd.), for example. In one embodiment, the metal powder preferablyhas an average particle size in the range of approximately 5 to 100 μm,more preferably approximately 10 to 80 μm.

In one embodiment, the metal powder may contain at least two, forexample, two, three, or four metal powders with different averageparticle sizes. The use of metal powders with different average particlesizes improves the magnetic characteristics of the magnetic body 11 andimproves the adhesiveness of the outer electrodes 31 and 32 formed byplating. In one embodiment, the use of an iron or iron alloy powder anda metal powder with a smaller average particle size than the iron oriron alloy powder can improve the magnetic characteristics of themagnetic body 11.

At least part of the metallic material is preferably exposed at thesurface of the magnetic body 11. The term “exposed,” as used herein,refers to being exposed at the surface of the magnetic body 11 and alsobeing exposed at an interface with another member. Thus, a metallicmaterial exposed at the surface of the magnetic body 11 may be coveredwith another member, for example, the outer electrodes 31 and 32 or theinsulation film 41, as discussed above. In a preferred embodiment, theratio of the exposed area of the metallic material to the surface areaof the magnetic body 11 may be approximately 20% or more, preferablyapproximately 30% or more. An increase in the exposed area results in anincrease in the electrical conductivity of the surface of the magneticbody 11 and thereby makes plating treatment easier.

The metallic material, typically a metal powder, preferably fuses andforms a network structure on the surface of the magnetic body 11. FIG. 3is a schematic cross-sectional view of the body illustrated in FIG. 2parallel to the LW-surface on the periphery of the coil conductor. FIG.4 is a schematic plan view of the periphery of the coil conductor 21 onthe end face 15. In FIG. 4, a metallic material 12 is exposed on theresin material 13 and forms a network structure. The network structureof the metallic material facilitates electric current supply in platingtreatment and increases the plating deposition rate. In a preferredembodiment, the metallic material, typically a metal powder, melts onceand fuses. This strengthens the network structure of the metallicmaterial and makes plating treatment easier. This can also prevent themetallic material from separating from the magnetic body 11 by cuttingor barrelling.

Even when the network structure of the metallic material is disposed onthe surface of the magnetic body 11, the magnetic body 11 includes nonetwork structure therein. Thus, the interior of the magnetic body 11can have insulating properties and maintain dielectric strength.

In one embodiment, a region on the surface of the magnetic body 11adjacent to the coil conductor 21 may be removed (see the left side ofthe coil conductor 21 in FIGS. 7C and 7D, for example). The removal ofthe region of the magnetic body 11 adjacent to the coil conductor 21increases the space between the magnetic body 11 and the coil conductor21, facilitates the infiltration of a medium in barrel plating, andimproves the plating deposition rate.

The coil conductor 21 is formed by winding a conducting wire containingan electrically conductive material. The electrically conductivematerial may be, but is not limited to, Au, Ag, Cu, Pd, or Ni.Preferably, the electrically conductive material is Cu. The electricallyconductive materials may be used alone or in combination.

The shapes of the conducting wire and the coil conductor 21 are notlimited to those illustrated in the figures and may be any shapesavailable for coil components. In the present embodiment, as illustratedin FIG. 2, the coil conductor 21 is wound as two layers such that theends 22 and 23 are disposed outwardly. Thus, the coil conductor 21 isformed by winding a rectangular conducting wire outwardly in layers. Theend 22 of the coil conductor 21 is exposed at the end face 15 of thebody 6, and the other end 23 of the coil conductor 21 is exposed at theother end face 16 of the body 6.

The conducting wire of the coil conductor 21 is covered with aninsulating film (the insulating film is not shown in FIG. 2). Typically,as illustrated in FIG. 3, an end portion of a lead portion of the coilconductor 21 to be connected to the outer electrodes 31 and 32 isexposed, and the other portion of the coil conductor 21 is covered withan insulating film 42. Thus, the coil conductor 21 is composed of anexposed portion 24 at each end portion thereof and a covered portion 25between the exposed portions 24. The conducting wire of the coilconductor 21 covered with the insulating film 42 can ensure insulationbetween the coil conductor 21 and the magnetic body 11. The exposed endportions of the coil conductor 21 make plating treatment easier, thusresulting in an outer electrode with little variation in thickness. Thiscan also reduce the resistance of the contact portions between the coilconductor 21 and the outer electrodes 31 and 32.

The insulating film 42 may be, but is not limited to, a film of apolyurethane resin, a polyester resin, an epoxy resin, or apolyamideimide resin. The insulating film 42 preferably has a thicknessof approximately 0.5 μm or more, more preferably approximately 1.0 μm ormore. The insulating film 42 having a thickness in this range can ensureinsulation between the coil conductor 21 and the magnetic body 11. Theinsulating film 42 preferably has a thickness of approximately 20 μm orless, more preferably approximately 10 μm or less, still more preferablyapproximately 5.0 μm or less. The insulating film 42 with a thickness inthis range can ensure a larger volume of the magnetic body 11 andimprove the magnetic characteristics of the coil component 1. In oneembodiment, the insulating film 42 may have a thickness in the range ofapproximately 0.5 to 20 μm, preferably approximately 1.0 to 10 μm, morepreferably approximately 1.0 to 5.0 μm.

The average length of the exposed portion 24 at each end portion in thelongitudinal direction of the conducting wire may preferably beapproximately 1 μm or more, more preferably approximately 5 μm or more,still more preferably approximately 10 μm or more, still more preferablyapproximately 20 μm or more. An average length of the exposed portion 24in this range can result in easier plating treatment, an improvedplating deposition rate, and a reduced unplated area. This can alsoresult in lower resistance of the contact portions between the coilconductor 21 and the outer electrodes 31 and 32. The exposed portion 24may preferably have an average length of approximately 100 μm or less,more preferably approximately 70 μm or less, still more preferablyapproximately 50 μm or less. The exposed portion 24 with an averagelength in this range can reduce the area of the contact portions betweenthe coil conductor 21 and the outer electrodes 31 and 32 within themagnetic body 11. Considering heat generation in the contact portions, adecrease in the area of the contact portions within the magnetic body 11can reduce heat generation in the magnetic body 11. In one embodiment,the exposed portion 24 may have an average length in the range ofapproximately 1 to 100 μm, preferably approximately 5 to 70 μm, morepreferably approximately 10 to 50 μm, still more preferablyapproximately 20 to 50 μm.

The phrase “the length of the exposed portion in the longitudinaldirection of the conducting wire,” as used herein, refers to the lengthfrom an end of the conducting wire in one end portion to the insulatingfilm in the longitudinal direction of the conducting wire (for example,Z1 and Z2 in FIG. 3). The phrase “the average length of the exposedportion in the longitudinal direction of the conducting wire,” as usedherein, refers to the average length around the conducting wire.

The maximum length of the exposed portion 24 at each end portion in thelongitudinal direction of the conducting wire may preferably beapproximately 1 μm or more, more preferably approximately 5 μm or more,still more preferably approximately 10 μm or more, still more preferablyapproximately 20 μm or more, for example, approximately 40 μm or more.When the exposed portion 24 has a maximum length in this range, platingon the coil conductor 21 can be more quickly coupled to plating on themagnetic body 11 over the insulating film 42 in plating treatment. Thus,the plating layers at both end portions (the outer electrodes 31 and 32)are electrically connected to each other via the coil conductor 21,thereby improving the plating deposition rate. The exposed portion 24may preferably have a maximum length of approximately 100 μm or less,more preferably approximately 80 μm or less, still more preferablyapproximately 60 μm or less. In one embodiment, the exposed portion 24may preferably have a maximum length in the range of approximately 1 to100 μm, more preferably approximately 5 to 80 μm, still more preferablyapproximately 10 to 60 μm, still more preferably approximately 20 to 60μm, for example, approximately 40 to 60 μm. The phrase “the maximumlength of the exposed portion in the longitudinal direction of theconducting wire,” as used herein, refers to the length of the longestpart of the exposed portion in the longitudinal direction of theconducting wire around the conducting wire.

The minimum length of the exposed portion 24 at each end portion in thelongitudinal direction of the conducting wire may preferably beapproximately more than 0 μm, more preferably approximately 1 μm ormore, still more preferably approximately 5 μm or more, still morepreferably approximately 10 μm or more, particularly preferablyapproximately 20 μm or more. A minimum length of the exposed portion 24in this range results in an improved plating deposition rate. Theexposed portion 24 may preferably have a minimum length of approximately100 μm or less, more preferably approximately 70 μm or less, still morepreferably approximately 50 μm or less. In one embodiment, the exposedportion 24 may preferably have a minimum length of more thanapproximately 0 μm and approximately 100 μm or less, more preferablyapproximately 1 to 70 μm, still more preferably approximately 5 to 50μm, still more preferably approximately 10 to 50 μm, particularlypreferably approximately 20 to 50 μm. The phrase “the minimum length ofthe exposed portion in the longitudinal direction of the conductingwire,” as used herein, refers to the length of the shortest part of theexposed portion in the longitudinal direction of the conducting wirearound the conducting wire.

The covered portion of the coil conductor 21 is disposed inside thefaces of the magnetic body 11 on which the outer electrodes 31 and 32are disposed, that is, the end faces 15 and 16. In other words, theexposed portions 24 of the coil conductor 21 extend to the inside of theend faces 15 and 16.

The average depth of each of the exposed portions 24 from the end faces15 and 16 may preferably be approximately 1 μm or more, more preferablyapproximately 5 μm or more, still more preferably approximately 8 μm ormore, still more preferably approximately 10 μm or more, particularlypreferably approximately 20 μm or more. An average depth in this rangecan result in easier plating treatment, an improved plating rate, and areduced unplated area. This can also reduce the resistance of thecontact portions between the coil conductor 21 and the outer electrodes31 and 32. The average depth may preferably be approximately 80 μm orless, more preferably approximately 50 μm or less, still more preferablyapproximately 35 μm or less. An average depth in this range can resultin improved dissipation of heat generated in the contact portionsbetween the coil conductor 21 and the outer electrodes 31 and 32. In oneembodiment, the average depth may preferably range from approximately 1to 80 μm, more preferably approximately 5 to 50 μm, still morepreferably approximately 8 to 35 μm, still more preferably approximately10 to 35 μm, particularly preferably approximately 20 to 35 μm.

The phrase “the depth of the exposed portion from the end face,” as usedherein, refers to the depth in a direction perpendicular to the end face(for example, Y1 and Y2 in FIG. 3). The reference position of the endface is the average height of a straight line between an edge of theexposed coil conductor on the end face and the nearest edge of the endface (the contact portions between the end faces 15 and 16 and the firstto fourth side surfaces 17 to 20 in FIG. 2) (except the portion 50 μm inlength from an edge of the coil conductor). The phrase “the averagedepth of the exposed portion from the end face,” as used herein, refersto the average depth of the exposed portion around the conducting wire.

The maximum depth of each of the exposed portions 24 from the end faces15 and 16 may preferably be approximately 1 μm or more, more preferablyapproximately 5 μm or more, still more preferably approximately 8 μm ormore, still more preferably approximately 10 μm or more, particularlypreferably approximately 20 μm or more. A maximum depth in this rangeresults in an improved plating rate. The maximum depth may preferably beapproximately 80 μm or less, more preferably approximately 50 μm orless, still more preferably approximately 40 μm or less. A maximum depthin this range can result in less heat generation in the contact portionsbetween the coil conductor 21 and the outer electrodes 31 and 32. In oneembodiment, the maximum depth may preferably range from approximately 1to 80 μm, more preferably approximately 5 to 50 μm, still morepreferably approximately 8 to 40 μm, still more preferably approximately10 to 40 μm, particularly preferably approximately 20 to 40 μm. Thephrase “the maximum depth of the exposed portion from the end face,” asused herein, refers to the depth of the deepest portion around theconducting wire.

The minimum depth of each of the exposed portions 24 from the end faces15 and 16 may preferably be more than approximately 0 μm, morepreferably approximately 3 μm or more, still more preferablyapproximately 5 μm or more, still more preferably approximately 7 μm ormore, still more preferably approximately 10 μm or more. A minimum depthin this range results in easier plating treatment and an improvedplating deposition rate. This can also reduce the resistance of thecontact portions between the coil conductor 21 and the outer electrodes31 and 32. The minimum depth may preferably be approximately 80 μm orless, more preferably approximately 50 μm or less, still more preferablyapproximately 30 μm or less. A minimum depth in this range can result inimproved dissipation of heat generated in the contact portions betweenthe coil conductor 21 and the outer electrodes 31 and 32. In oneembodiment, the minimum depth may preferably be more than approximately0 μm and approximately 80 μm or less, more preferably approximately 3 to50 μm, still more preferably approximately 5 to 30 μm, still morepreferably approximately 7 to 30 μm, particularly preferablyapproximately 10 to 30 μm. The phrase “the minimum depth of the exposedportion from the end face,” as used herein, refers to the depth of theshallowest portion around the conducting wire.

The cross sections of the ends 22 and 23 of the coil conductor 21 arepreferably flush with or disposed outside the faces of the magnetic body11 on which the outer electrodes 31 and 32 are disposed, that is, theend faces 15 and 16. More preferably, the cross sections of the ends 22and 23 of the coil conductor 21 are disposed outside the faces of themagnetic body 11 on which the outer electrodes 31 and 32 are disposed.In other words, the ends 22 and 23 of the coil conductor 21 protrudefrom the end faces 15 and 16.

The average protrusion height of each of the ends of the coil conductor21 from the end faces 15 and 16 may preferably be approximately 0 μm ormore, more preferably approximately 1 μm or more, still more preferablyapproximately 5 μm or more, still more preferably approximately 10 μm ormore, for example, approximately 15 μm or more. For an averageprotrusion height in this range, the contact portions between the coilconductor 21 and the outer electrodes 31 and 32 can be disposed outsidethe body. Thus, heat generated in the contact portions can be moreeasily dissipated. This also improves the plating deposition rate. Theaverage protrusion height may preferably be approximately 80 μm or less,more preferably approximately 50 μm or less, still more preferablyapproximately 30 μm or less, still more preferably approximately 20 μmor less. For an average protrusion height in this range, the outerelectrodes 31 and 32 can be more easily flattened. In one embodiment,the average protrusion height may preferably range from approximately 0to 80 μm, more preferably approximately 1 to 50 μm, still morepreferably approximately 5 to 30 μm, still more preferably approximately10 to 20 μm, for example, approximately 15 to 20 μm.

The phrase “the protrusion height of the end of the coil conductor fromthe end face,” as used herein, refers to the protrusion height in adirection perpendicular to the end face (for example, X1 and X2 in FIG.3). The reference position of the end face is defined in the same manneras in the depth of the exposed portion from the end face. The phrase“the average protrusion height of the end of the coil conductor from theend face,” as used herein, refers to the average protrusion heightaround the conducting wire.

The maximum protrusion height of each of the ends of the coil conductor21 from the end faces 15 and 16 may preferably be approximately 1 μm ormore, more preferably approximately 5 μm or more, still more preferablyapproximately 10 μm or more, for example, approximately 15 μm or more. Amaximum protrusion height in this range results in improved heatdissipation and an improved plating deposition rate. The maximumprotrusion height may preferably be approximately 80 μm or less, morepreferably approximately 50 μm or less, still more preferablyapproximately 30 μm or less, still more preferably approximately 20 μmor less. For a maximum protrusion height in this range, the outerelectrodes 31 and 32 can be more easily flattened. In one embodiment,the maximum protrusion height may preferably range from approximately 1to 80 μm, more preferably approximately 5 to 50 μm, still morepreferably approximately 10 to 30 μm, for example, approximately 15 to20 μm. The phrase “the maximum protrusion height of the end of the coilconductor from the end face,” as used herein, refers to the height ofthe highest portion around the conducting wire.

The minimum protrusion height of each of the ends of the coil conductor21 from the end faces 15 and 16 may preferably be more thanapproximately 0 μm, more preferably approximately 1 μm or more, stillmore preferably approximately 3 μm or more, still more preferablyapproximately 5 μm or more, particularly preferably approximately 7 μmor more, particularly more preferably approximately 10 μm or more. Aminimum protrusion height in this range results in an improved platingdeposition rate. The minimum protrusion height may preferably beapproximately 60 μm or less, more preferably approximately 40 μm orless, still more preferably approximately 30 μm or less, still morepreferably approximately 20 μm or less. In one embodiment, the minimumprotrusion height may preferably be more than approximately 0 μm andapproximately 60 μm or less, more preferably approximately 1 to 40 μm,still more preferably approximately 3 to 30 μm, still more preferablyapproximately 5 to 20 μm, particularly preferably approximately 7 to 20μm, particularly more preferably approximately 10 to 20 μm. The phrase“the minimum protrusion height of the end of the coil conductor from theend face,” as used herein, refers to the height of the lowest portionaround the conducting wire.

In one embodiment, the coil conductor 21 may have a round end portion(see FIG. 7D). The coil conductor 21 with a round end portion increasesthe space between the magnetic body 11 and the coil conductor 21,facilitates the infiltration of a medium in barrel plating, and improvesthe plating deposition rate.

In the present embodiment, the coil conductor 21 has oblique ends 22 and23. In other words, the angle of each cross section of the ends 22 and23 of the coil conductor 21 to the central axis of the conducting wireof the coil conductor 21 is less than approximately 90 degrees. Thephrase “the angle of the cross section of the end of the coil conductorto the central axis of the conducting wire of the coil conductor,” asused herein, refers to the minimum angle between the cross section andthe central axis.

The angle is preferably approximately 30 degrees or more, morepreferably approximately 40 degrees or more, still more preferablyapproximately 50 degrees or more. The angle can be increased to reducethe area behind the coil conductor 21 during the removal of theinsulating film 42 from the conducting wire by laser irradiation, thusmaking the removal easier. The angle is preferably approximately 80degrees or less, more preferably approximately 70 degrees or less, stillmore preferably approximately 60 degrees or less. The angle can bedecreased to increase the cross-sectional area at each end of the coilconductor 21, thus making plating easier and reducing the unplated area.This can also increase the contact areas between the coil conductor 21and the outer electrodes 31 and 32 and decrease resistance in thecontact portions. In one embodiment, the angle preferably ranges fromapproximately 30 to 80 degrees, more preferably approximately 40 to 70degrees, still more preferably approximately 50 to 60 degrees. In thepresent disclosure, the coil conductor does not necessarily have anoblique end and may have a cross section perpendicular to the centralaxis.

For the coil conductor 21 with an oblique end, in a section of the coilcomponent 1 in the longitudinal direction of the conducting wire of thecoil conductor 21 (for example, a section parallel to the LW-surface inFIG. 2), the angle between a surface (outer surface) of the magneticbody 11 and the coil conductor 21 of the magnetic body 11 (for example,the angles α and β in FIG. 3) varies from an obtuse angle to an acuteangle depending on the section. Preferably, the magnetic body 11 is moreeasily removed in a region with an acute angle (for example, the angle αin FIG. 3) than in a region with an obtuse angle (for example, the angleβ in FIG. 3) on the surface of the magnetic body 11 adjacent to the coilconductor 21. Preferably, the coil conductor 21 has a more round endportion in the region with an acute angle than in the region with anobtuse angle.

The outer electrodes 31 and 32 are disposed on the outer surface of thebody 6. Preferably, the outer electrodes 31 and 32 are formed by platingtreatment. The outer electrodes 31 and 32 may be monolayer ormultilayer. The outer electrodes 31 and 32 are formed of an electricallyconductive material, preferably at least one metallic material selectedfrom Au, Ag, Pd, Ni, and Cu.

In the present embodiment, the outer electrodes 31 and 32 are disposedon the end faces 15 and 16, respectively, and extend to a portion of thefourth side surface 20. The outer electrode 31 is electrically connectedto the end 22 of the coil conductor 21, and the outer electrode 32 iselectrically connected to the end 23 of the coil conductor 21. The outerelectrodes 31 and 32 may have any thickness, for example, in the rangeof approximately 1 to 20 μm, preferably approximately 5 to 10 μm.

In the present embodiment, the insulation film 41 is disposed in aregion on the outer surface of the body 6 where the outer electrodes 31and 32 are not disposed. The insulation film 41 may be formed of aninsulating resin material, such as an acrylic resin, an epoxy resin, orpolyimide. In the present disclosure, an insulation film is notessential and may be omitted.

A method for producing the coil component 1 will be described below.

The body 6 is produced. The body 6 can be produced by placing the coilconductor 21 in the magnetic body 11. For example, the body 6 can beproduced as described below.

The coil conductors 21 are placed in a mold. A sheet of a compositematerial containing a metallic material and a resin material is thenplaced on the coil conductors 21 and is subjected to first pressforming. At least part of the coil conductors 21 is embedded in thesheet by the first press forming. The coil conductors 21 are filled withthe composite material.

The sheet including the coil conductors 21 after the first press formingis removed from the mold. Another sheet is then placed on a bare surfaceof the coil conductors 21 and is subjected to secondary pressing. Thus,a coil assembly substrate including the bodies 6 is produced. The twosheets are integrated by the secondary pressing and constitute themagnetic body 11 of the coil component 1.

The coil assembly substrate formed by the secondary press forming wasdivided into the bodies 6. The ends 22 and 23 of the coil conductor 21are exposed at the opposite end faces 15 and 16 of each of the bodies 6.

The coil assembly substrate can be divided into the bodies 6 with adicing blade, a laser apparatus, a dicer, a cutting tool, or a mold. Ina preferred embodiment, the cut surfaces of the bodies 6 are subjectedto barrel polishing.

A method for producing the body 6 of the coil component 1 according toan embodiment of the present disclosure has been described. However, thebody 6 can be produced not only by this method but also by any method bywhich a body including a coil conductor in a magnetic body can beproduced. For example, a coil conductor paste and a metal powder pasteare repeatedly applied by screen printing to form a block, and the blockis divided into pieces and fired. Alternatively, a coil conductor may beembedded in a core of a composite material.

The outer electrodes 31 and 32 are then formed by plating treatment,preferably electroplating treatment, on the end faces 15 and 16 at whichthe ends 22 and 23 of the coil conductor 21 are exposed. The ends 22 and23 of the coil conductor 21 are electrically connected to the outerelectrodes 31 and 32, respectively. Thus, a coil component according toan embodiment of the present disclosure is produced.

A plating treatment will be described in detail below.

The insulation film 41 is formed on the outer surface of the body 6. Aportion of the insulation film 41 in the regions on the outer surface ofthe body 6 in which the outer electrodes 31 and 32 are to be formed isthen removed. Methods for forming and removing the insulation film 41can be known methods. For example, the insulation film 41 can be formedby spraying or dipping.

A peripheral portion of the coil conductor 21 exposed at the surface ofthe magnetic body 11 is then irradiated with a laser beam. Thus, theinsulating film 42 is removed from the end portions of the coilconductor 21 to form the exposed portions 24 extending to the inside ofthe end faces 15 and 16 of the magnetic body 11.

Thus, the present disclosure also provides a method for producing a coilcomponent that includes a magnetic body containing a metallic materialand a resin material, a coil conductor embedded in the magnetic body,and a pair of outer electrodes electrically connected to ends of thecoil conductor. The method includes treating a peripheral portion of thecoil conductor by laser irradiation, the peripheral portion beingexposed at a surface of the magnetic body, and then forming the outerelectrodes by plating treatment.

In a preferred embodiment, laser irradiation is performed in the entireregion of the outer surface of the body 6 in which the outer electrodes31 and 32 are to be formed. The insulation film 41 in the regions of theouter surface of the body 6 in which the outer electrodes 31 and 32 areto be formed may be simultaneously removed by the irradiation.

At least part of the resin material of the magnetic body 11 is removedfrom the laser-irradiated surface of the magnetic body 11, and at leastpart of the metallic material (typically a metal powder) can fuse. Thus,the metallic material can form a network structure on the surface of themagnetic body 11. The intensity of laser irradiation can be controlledto melt and fuse the metallic material (typically a metal powder) on thesurface of the magnetic body 11.

Even when the metallic material forms a network structure on the surfaceof the magnetic body 11 by laser irradiation, no network structure isformed within the magnetic body 11. Thus, the interior of the magneticbody 11 can have insulating properties and maintain dielectric strength.

The laser-irradiated surface of the magnetic body 11, from which theresin material and the metallic material are removed, may be depressedby laser irradiation. Thus, the ends 22 and 23 of the coil conductor 21may protrude from the surface of the magnetic body 11.

In a preferred embodiment, a region on the surface of the magnetic body11 adjacent to the coil conductor 21 may be removed by laserirradiation. The coil conductor 21 may have a round end portion due tolaser irradiation.

The laser wavelength in the laser irradiation ranges from approximately180 to 3000 nm, for example. The laser wavelength preferably ranges fromapproximately 532 to 1064 nm. Laser irradiation with a laser wavelengthin this range can remove an insulating film from a coil conductor withless damage to a body and thereby increase the plating rate. The laserwavelength is determined in consideration of damage to a body and areduction in processing time. The laser radiation energy is preferablyapproximately 0.20 J/mm² or more, more preferably approximately 0.35J/mm² or more, still more preferably approximately 0.45 J/mm² or more,still more preferably approximately 0.50 J/mm² or more, for example,approximately 0.60 J/mm² or more. Laser radiation energy in this rangeresults in more efficient removal of an insulating film and a resinmaterial of a magnetic body and better formation of a network structureof a metallic material of a magnetic body. The laser radiation energymay preferably be approximately 3.0 J/mm² or less, more preferablyapproximately 2.0 J/mm² or less, still more preferably approximately 1.5J/mm² or less, for example, approximately 1.0 J/mm² or less. Laserradiation energy in this range can have less damage to a body. In oneembodiment, the laser radiation energy may preferably range fromapproximately 0.20 to 3.0 J/mm², more preferably approximately 0.35 to2.0 J/mm², still more preferably approximately 0.45 to 1.5 J/mm², stillmore preferably approximately 0.50 to 1.0 J/mm², particularly preferablyapproximately 0.60 to 1.0 J/mm².

In one embodiment, the surfaces to be irradiated with a laser beam arethe end faces 15 and 16 of the body 6 on which the insulation film 41 isformed, a portion of the fourth side surface 20 adjacent to the end face15, and a portion of the fourth side surface 20 adjacent to the end face16. The insulation film 41 is removed from the laser-irradiated regions.The insulating film 42 at the end portions of the coil conductor 21 isalso removed. The resin material on the surface of the magnetic body 11may be removed from the laser-irradiated surface, thereby exposing themetallic material. The insulation film 41, the resin material on thesurface of the magnetic body 11, and the insulating film 42 at the endsof the coil conductor 21 may be removed by laser irradiation.

The outer electrodes 31 and 32 (plating layers) are then formed byplating on the laser-irradiated surface of the body 6. Morespecifically, the outer electrode 31 is continuously formed on the endface 15 and a portion of the fourth side surface 20 adjacent to the endface 15, and the outer electrode 32 is continuously formed on the endface 16 and a portion of the fourth side surface 20 adjacent to the endface 16.

In the plating treatment of the body 6, a plating layer is deposited onthe exposed metallic material and the exposed portions of the coilconductor 21 and gradually cover the entire laser-irradiated surface,thereby forming the substantially L-shaped outer electrodes 31 and 32. Aplating catalyst may be applied to the laser-irradiated surface of thebody 6 before plating treatment to form a plating film. The platingcatalyst is a metal that improves the deposition rate of a platinglayer, for example, a metal solution or a nanoscale metal powder ormetal complex.

The plating metal may be of any type, for example, Au, Ag, Pd, Ni, orCu, preferably Pd, Ag, or Cu. In the case where the outer electrodes 31and 32 are multilayer, for example, a Ni plating layer and a Sn platinglayer are preferably formed on the plating layer. The plating method ispreferably, but not limited to, barrel plating.

In the present disclosure, no insulating film is disposed between themagnetic body 11 and the coil conductor 21 in the surface portion of thebody 6. Thus, the magnetic body 11 is electrically connected to the coilconductor 21 via the plating layer in a short time after the beginningof plating treatment. Thus, the plating layers on the end faces 15 and16 of the body 6 are electrically connected to each other via the coilconductor 21. This improves the plating deposition rate and reducesvariations in plating deposition rate on the end faces 15 and 16. Inparticular, at least part of the metallic material in the platingportion that fuses to form a network structure facilitates electriccurrent supply and improves the deposition rate of the plating layer.

Although the coil components and the methods for producing the coilcomponents according to the embodiments of the present disclosure aredescribed above, the present disclosure is not limited to theseembodiments, and these embodiments may be modified without departingfrom the gist of the present disclosure. For example, although the coilconductor 21 of the coil component 1 is disposed such that the centralaxis of the coil conductor 21 is perpendicular to the end faces 15 and16, the coil conductor 21 of the coil component 1 may be disposed suchthat the central axis of the coil conductor 21 is parallel to the endfaces 15 and 16.

A portion on the end face 15 of the outer electrode 31 and a portion onthe end face 16 of the outer electrode 32 may be covered with theinsulation film 41, and only portions of the outer electrodes 31 and 32on the fourth side surface 20 may be exposed. Thus, the substantiallyL-shaped outer electrodes 31 and 32 may be outer electrodes on onesurface (bottom electrodes).

EXAMPLES

Fe—Si was prepared as a metal powder, and a composite sheet containingan epoxy resin was prepared as a resin material. α-coiled conductors(coil conductors formed by winding a rectangular conducting wireoutwardly in two layers) made of copper were prepared. Each of theα-coiled conductors was covered with a polyurethane resin serving as aninsulating material.

The α-coiled conductors were then placed on a mold. The composite sheetwas placed on the α-coiled conductors and was pressed for approximately30 minutes at a pressure of approximately 5 MPa and at a temperature ofapproximately 150° C.

The composite sheet combined with the coil conductors was then removedfrom the mold. Another composite sheet was placed on the surface atwhich the coil conductors were exposed, and was pressed forapproximately 30 minutes at a pressure of approximately 5 MPa and at atemperature of approximately 150° C. to form a coil assembly substrateincluding the coil conductors.

The coil assembly substrate was divided into bodies with a dicing blade.The bodies were subjected to barrel polishing. The ends of the coilconductors were exposed at the opposite side surfaces (end faces) of thebodies.

The areas of the body in which outer electrodes were to be formed werethen irradiated with a laser beam. The laser was a YVO₄ laser(wavelength: approximately 532 nm), and the radiation energy wasapproximately 0.25, 0.36, 0.46, 0.56, or 0.68 J/mm². After laserirradiation, observations of the irradiated surface with a scanningelectron microscope (SEM) showed that the insulating layer on thesurface of the body was removed, and the metal powder was exposed on theresin material, melted, and fused to form a network structure. FIG. 5(approximately 0.25 J/mm²) and FIG. 6 (approximately 0.68 J/mm²) showlaser-irradiated body surfaces.

Cu plating was then performed for approximately 180 minutes with abarrel electroplating apparatus at a current value of approximately 15 Aand at a temperature of approximately 55° C. to form outer electrodes onthe laser-irradiated surfaces. Thus, a coil component according to anembodiment of the present disclosure was produced.

Evaluation

Cross-Sectional Shape of Periphery of Conductor

The coil components thus produced were stood such that the LW-surfaceswere exposed, and were enclosed with a resin. The LW-surfaces werepolished with a polisher up to almost the center of an end of the coilconductor. The cross-sectional shape of the periphery of the conductorwas observed with the scanning electron microscope. As illustrated inFIG. 3, the protrusion height X1 from the end face and the depth Y1 ofthe exposed portion from the end face were measured on the side on whichthe angle between the surface (outer surface) of the magnetic body andthe coil conductor was an acute angle (on the angle α side in FIG. 3).Likewise, the protrusion height X2 from the end face and the depth Y2 ofthe exposed portion from the end face were measured on the side on whichthe angle between the surface of the magnetic body and the coilconductor was an obtuse angle (the angle β side in FIG. 3). Table 1lists the average values of ten of the coil components for eachradiation energy. The sample number 1 is a comparative example.

TABLE 1 Radiation energy X1 Y1 X2 Y2 Sample No. (J/mm²) (μm) (μm) (μm)(μm) *1  0 0 0 0 0 2 0.25 0 6 0 3 3 0.36 0 9 0 5 4 0.46 5 10 3 7 5 0.5610 20 6 11 6 0.68 15 30 9 15

Table 1 shows that in the sample number 1 (no laser irradiation) theinsulating film was not removed, and the insulating film and the end ofthe coil conductor had the same height (FIG. 7A). In the sample numbers2 and 3 (approximately 0.25 and 0.36 J/mm²), although the insulatingfilm was removed at the end portion of the coil conductor, therebyforming an exposed portion, the end face of the magnetic body and theend of the coil conductor had the same height (FIG. 7B). In the samplenumber 4 (approximately 0.46 J/mm²), the insulating film was removed atthe end portion of the coil conductor, thereby forming an exposedportion, and the end of the coil conductor was higher than the end faceof the magnetic body (FIG. 7C). In the sample numbers 5 and 6, the coilconductor had a round end (FIG. 7D).

Deposition of Plating

For each radiation energy, the appearances of 100 of the coil componentswere checked for deposition of plating. The number of components with anunplated area of 50% or more of the laser-irradiated region was countedas “unplated.” Table 2 shows the results.

Deposition Rate (Plating Deposition Rate)

The cross sections of the coil components were polished, and thethicknesses were measured at five points with a fluorescent X-ray filmthickness gauge (SFT3500 manufactured by Seiko Instruments Inc.). Theaverage of the thicknesses was divided by the plating time to calculatethe deposition rate. Table 2 lists the average values of ten of the coilcomponents for each radiation energy.

TABLE 2 Radiation Plating Number of energy thickness Deposition rateunplated Sample No. (J/mm²) (μm) (μm) components *1  0 0.3 0.2 × 10⁻²100/100  2 0.25 6.2 3.4 × 10⁻² 50/100  3 0.36 8.6 4.8 × 10⁻² 10/100  40.46 9.9 5.5 × 10⁻² 0/100 5 0.56 10.4 5.8 × 10⁻² 0/100 6 0.68 10.7 5.9 ×10⁻² 0/100

As is clear from Table 2, in the sample number 1 with no laserirradiation, all the coil components were unplated. By contrast, thenumber of unplated coil components decreased in the sample numbers 1 to6 with laser irradiation. In particular, plating was good in all thecoil components of the sample numbers 4 to 6. In particular, thedeposition rate was also good in the sample numbers 5 and 6.

A coil component according to an embodiment of the present disclosurecan be widely used as an inductor or another device in variousapplications.

While preferred embodiments of the disclosure have been described above,it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the disclosure. The scope of the disclosure, therefore, isto be determined solely by the following claims.

What is claimed is:
 1. A method for producing a coil component thatincludes a magnetic body containing a metallic material and a resinmaterial, a coil conductor embedded in the magnetic body, and a pair ofouter electrodes electrically connected to ends of the coil conductor,the method comprising: treating a peripheral portion of the coilconductor by laser irradiation, the peripheral portion being exposed ata surface of the magnetic body; and then forming the outer electrodes byplating treatment.
 2. The method according to claim 1, wherein the laserirradiation depresses the surface of the magnetic body at which theperipheral portion of the coil conductor is exposed.
 3. The methodaccording to claim 1, wherein the laser irradiation forms a round endportion at the peripheral portion of the coil conductor.
 4. The methodaccording to claim 1, further comprising applying a plating catalyst maybe applied to the laser-irradiated peripheral portion before forming theouter electrodes by the plating treatment.
 5. The method according toclaim 1, wherein the plating treatment forms a plating layer that formsthe outer electrodes and electrically connects the magnetic body to thecoil conductor.